Who knows? It says "Unsupported operating system". Of course, it might not have liked curl on cygwin on Win7 at the best of times, but IE 11 gives the same result, and surely it would like that if it liked anything. But whether this is by accident or design, I can't guess. Maybe it's their way of suggesting you use deploy.js (see Java Rich Internet Applications Deployment Advice).
$ curl -I http://java.sun.com/products/autodl/j2se
HTTP/1.0 301 Moved Permanently
20 Unsupported operating system
HTTP/1.1 200 OK
Server: Sun Java System Web Server 6.1
Date: Fri, 14 Feb 2014 10:20:18 GMT
Thanks for the reply.
I guess the javaws auto download feature is going the way of the Dodo.